1. Field of the Invention
This invention relates to the field of disk drive suspensions. More particularly, this invention relates to the field of a low resistance interface metal for disk drive suspension component grounding.
2. Description of Related Art
Good electrical connections must be made between a suspension's stainless steel (SST) body on the one hand, and other components such as suspension flexure circuit bond pads, grounding wires, flying leads, or microactuators such as piezoelectric (PZT) devices on the other hand. Microactuators are used to cause very fine control and movement of the suspension's read/write head, and are often mounted directly to the mount plate.
One prior art method of creating that electrical connection is by using silver (Ag) epoxy as an adhesive between the mount plate, which is grounded, and the other component. However, the inherently chromium (Cr) rich passivation layer which forms on the surface of the stainless steel tends to create a high resistance barrier on that surface. Some of the silver epoxies that have been used in the past as conductive adhesives suffer the drawback of having a resistance that increases in response to temperature, humidity, and/or time. One of the silver epoxies whose resistance increases the least over temperature, humidity, and time, suffers the additional disadvantage of containing mercury which must be handled as a hazardous material.
Designing a low resistance interconnect from the PZT to the mount plate is further complicated by the inherent mechanical strain induced by the 20 nm/V displacement of the PZT when driven up to 20 volts at an operational frequency of 1-30 KHz, which renders connections which rely on soft materials such as solder inadequate for the demanding cyclic loads experienced at the PZT/mount plate interface.